Wireless client keep loosing IP address.

Question

Hi,
I am in hot water, i am not good with wireless i have wireless LAN in my network which is connected to wired network. the problem is my clients get connected to the network but suddently they loose connectivity and start dhcp request and get limited connecitivity with automatic ip address.
My network design is like this.
1. I have a three floor building every floor has its own core and access layer and floors are connected layer 3 (not usual layer 2).
2. Wireless Controllers 4402 are in layer 3 mode and are on ground floor and AP are everywhere in building.
3. Wireless controllers are connected to ground floor core using a VLAN say VLAN 205 and AP's on ground floor and other floors are in different VLANs (physical connectivity of AP's).
4. controllers are configured for two different VLAN's say VLAN 212 for data and VLAN 213 for voice.
5. VLAN interface of the controller is configured with right helper address for DHCP.
My problem is i am a bit confused with the desigh of the network. As i mentioned all floors are connected layer 3 it means seperate VTP domain and seperate VLAN's, all APs on all floors are in differnt IP subnet respectively. but the wireless VLAN is common for all the users on all floors, this is the bit which confuses me alot. the wireless data VLAN has its own IP subnet which is advertised from gound floor only (make sense) but the users are not connecting to ground floor APs only they are connecting everywhere in the building. Users are getting IP address from the wireless VLAN range on every floor, can anybody explain me how they are getting communication because wireless subnet is only local to ground floor core not to first floor or second floor but some people are connecting to 1st floor and 2nd floor AP and are working fine.
The next pain is that my laptops started loosing IP address and they get automatic private IP address hence loose connectivity, the communication issue i referred above is secondary i am actually looking to rectify the ip address issue because users are having problem with it. Signal strength on every floor is perfect and coverage is ok, i have tried to debug dhcp detail packet but i don't receive any because controllers are in differnt VLAN for physical connectivity. Can somebody help me with this thing?
Regards,

Answer 1

Your wireless clients will associate to the best AP interms of signal strenght and signal to noise etc.
There is an LWAPP tunnel between the access point and the controller.
At the controller there will be logical interfaces for the wireless LANS that are asssociated to specific VLANs on the wired network.
It doesn't matter where you are in the building as a client as its the controller that puts the client data onto the wired network.
All client data is tunneled between the access point and the controller.
With regard to the losing IP address situation. I assume that the clients do initially get an IP address and then lose it after a period of time.
Check the session timeout paramter on the controller (look on the WLAN-Advanced).
There is a bug with some versions of software relating to session timeouts. Try setting the timeout to 65535 seconds. The default setting is probably 30 minutes.